1. Field of the Invention
The present invention relates to a method for removing a mottled etch in a semiconductor fabricating process, and more particularly, to a method for preventing mottled etch from being generated after etching, by performing ashing using an oxide plasma, prior to performing wet etching using a photoresist pattern.
2. Discussion of the Related Art
In general, a process for fabricating an oxide film provided in a high voltage semiconductor device includes the steps of depositing a high voltage gate oxide film, forming a photoresist pattern, and performing wet etch. In other words, the gate oxide film pattern is formed by performing wet etching using the photoresist pattern as an etch mask. In this instance, buffered hydrofluoric acid (BHF) is normally used as an etch solution. However, in the process of removing the oxide film using the etch solution, the solution reacts to the photoresist or oxide film and changes into a hydrophilic or hydrophobic solution.
When the etch solution changes into the hydrophobic solution, a wetting angle on a surface is increased by the hydrophobic reaction, and a bubble phenomenon of the etch solution results, whereby a mottled etch or a blue spot occurs.
FIG. 1 illustrates a microphotograph showing a mottled etch with various patterns on a surface of the semiconductor device. The mottled etch acts as a partial obstacle so as to form an inconsistent oxide film, or reacts to the air so as to contaminate an oxide film. If the mottled etch is not removed, problems are occurred in many subsequent processes such as ion implantation, thereby lowering the performance characteristic of the semiconductor device.